Renee Gracie is planning a spectacular return to the sport.
The Kiwi had his worst result of the season, but still holds a 107-point advantage.
The Kiwi driver came home fifth after starting 17th.
NZ's Liam Lawson was uninjured as his car caught fire during a race.
The Kiwi won a strategic opening night race at the Sydney SuperSprint.
The Kiwi started 17th, but a superb strategy paid off for the series leader.
Scott Dixon remains atop the standings, despite finishing 12th at Wisconsin.
The Kiwi is unbeaten this season with his third consecutive win.
The BBC claims the Spaniard has signed with Renault.